


Chain Reaction

by la_muerta



Series: Shadowhunter Bingo entries [4]
Category: Shadowhunters (TV)
Genre: Alternate Universe - This World Inverted (Shadowhunters TV), Barebacking, Bondage, Fuck Or Die, M/M, Porn With Plot, Porn with Feelings, Sex Pollen, Shadowhunter Bingo 2019
Language: English
Status: Completed
Published: 2020-03-19
Updated: 2020-03-19
Packaged: 2021-02-28 22:15:40
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 4,562
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23214658
Author URL: https://archiveofourown.org/users/la_muerta/pseuds/la_muerta
Summary: When shadowhunter Clary from the other dimension comes crashing into Magnus' simple, boring, magicless existence and awakens Magnus' dormant magic, she awakens a lot more than that.For the Shadowhunter Bingo Square:Fuck or Die
Relationships: Alternate Magnus Bane/Alternate Alec Lightwood (Shadowhunters: This World Inverted)
Series: Shadowhunter Bingo entries [4]
Series URL: https://archiveofourown.org/series/1570297
Comments: 39
Kudos: 345
Collections: SHBingo





	Chain Reaction

Magnus hadn't realised how much he'd given up when he'd made the decision to let his magic fade away. 

More than two hundred years ago, the Nephilim had made the bold decision to sacrifice their own angelic blood in a spell that sealed their world off from all the other realms - Demonic, Angelic, and Seelie. Magnus had been one of the warlocks who had agreed to help with the risky endeavour, keeping the Seelie Queen in the dark until it was too late for her to stop the spell. But being cut off from the demonic realms had also weakened the warlocks, who received their powers from their connection with their demon parents; the werewolf population had dwindled and died out; and only the craftiest vampires had learnt how to survive in a magicless world, hiding their nature under the fluorescent lights of the sleepless city and feeding discreetly. In one fell swoop, the Shadow World had been almost completely decimated. 

It hadn't been easy getting used to the new world order, even though the warlocks were now the largest remaining downworld faction. No new warlocks would be made, and the ones that were left were still immortal and eternal but only a shadow of their former selves. Some of the warlocks, like Catarina, had decided to live almost entirely like mundanes, taking on normal jobs and trying their best to blend in. Some of them had retreated into isolation, like Ragnor, and some of these had completely faded away. Others had gone mad and gone out in a blaze of chaos and hellfire, ending their immortal lives and leaving behind a headache of a mess for others to clean up. Magnus had cleaned up those messes for the most part of a century until his heart and mind had grown so weary, he'd decided to take a leaf out of Catarina's book. 

He'd bought a nice apartment in Brooklyn and settled down. No more using magic for big things like potions and spells for clients or his own amusement, then he'd given up using magic for little things as well, like chores and doing his eyeliner. A part of him had hoped that maybe letting his magic go would cause him to lose his immortality as well and become fully mortal, but his face in the mirror looked the same every day, never ageing. (Maybe that had been because some habits died hard, and Magnus could never let go of his magic completely - he could never have gone anywhere without glamouring his cat eyes.) Being without clients and things to keep himself busy had never been his style, so he'd started his tarot card reading business and a small underground trade in simple potions, and a few decades had passed in peace and quiet - until a red-haired girl had come into his house talking about shadowhunters and demons and waving interdimensional portal shards around. 

Now, with the portal shard Clary had given him he had magic at his fingertips again, and while he wasn't quite the force of nature he'd been in the past, it was more magic than he'd had for decades, and it was intoxicating. His connection to the energies of everything around him was singing in his blood and in his head, and for the first time in a long time, he felt like he was _alive_ , not just going through the motions of eating and breathing and existing. The first thing he'd done when he got home from the party at The Institute was to banish his entire wardrobe of cardigans and stuffy-professor jackets with matching trousers in varying shades of beige and brown. He'd stared at the emptiness in a mixture of horror and exhilaration, then gone on an online shopping spree.

Over the next few days, parcels began to arrive. He wasn't confident enough for leather jackets and pink hair yet, but he'd bought a number of patterned silk shirts in dark colours, sharper suits, as well as some soft scarves to dress things up a bit. He'd also gotten some black eyeliner, his old comfort armour, and with enough magic to put it on with a snap of his fingers, he'd started to feel a bit more like the man he'd once been. Maybe he'd start selling more complicated potions again, or travel the world and visit some old friends.

He was just looking up the prices of plane tickets to Devon, where Ragnor had sequestered himself, when his doorbell rang. Assuming it was another one of his numerous shopping deliveries, Magnus had opened the door without checking, and was surprised to find a handsome young man standing on his doorstep. It took only a moment for him to place him as the man who had let him into the party at The Institute, the one with a last name that marked him as one of the descendants of the Nephilim who no longer had angelic blood in their veins.

He shouldn't have been here. After extracting the portal shard to deactivate the door between the worlds, Magnus had stayed with this world's version of Clary and her boyfriend only long enough to make sure that the blond boy was ok, then he'd made his excuses and escaped. Clary hadn't remembered him at all, and Magnus tried not to have dealings with shadowhunters, angel blood or not. Magnus adjusted his collar to make sure that the portal shard that he now wore around his neck was out of sight, in case his visitor recognised it as the one Clary had been wearing. 

"Wow," his unexpected visitor said, raising his eyebrow as he took in Magnus' new outfit and eyeliner, as well as the new spikier hairstyle he was experimenting with. "You look different."

Magnus resisted the urge to flatten his hair. "I wanted to try something new."

"Well, it's definitely working for me," he said with a wink.

Magnus laughed a little self-consciously. "Um, it's Mr Lightwood, right? Thank you for letting me into your party the other night. Is there anything I can do for you?"

"Please call me Alec," he replied. "I found your address from your ad, and I came for a tarot card reading... and to apologise."

"For?" Magnus asked in confusion.

"It occurred to me that I came on a little too strong the other night," Alec said, dropping his flirty demeanour and suddenly looking very serious. "I'd assumed that the interest was mutual, but even if it was, maybe you didn't appreciate me putting you on the spot like that. Not everyone is lucky enough to have the support of their family and friends and a safe space to be themselves." 

Magnus blinked. "You thought that I wasn't out?"

"You practically ran away from me. What was I to think?" Alec asked. 

Magnus found himself exceedingly charmed that this boy, who couldn't be older than 25, had been worried about outing _Magnus_ , who had been openly bisexual for the most part of the four hundred years that he'd been alive even when it wasn't necessarily the wisest thing to do. It seemed like repressing his magic had resulted in him repressing a lot of other things as well. Magnus smiled at Alec and stepped aside to let him in.

"Thank you. I think I'm finally remembering how to be myself again, though. Please come in. I'll give you a reading on the house."

\--

One free tarot card reading became an invitation to dinner as repayment for the free reading, then an invitation to the movies, and before Magnus knew it, he was on his third date with Alec, to a bowling alley of all places. Despite the initial impression he'd given Magnus of being overconfident and a little bit pushy, Magnus had found Alec to be really quite sweet and considerate. It had been a while since he'd gone out with anyone, but he could get used to Alec pulling out chairs and opening doors for him, and on every date, Alec would bring him a single red rose, which Magnus would preserve with magic and carefully place in a vase in his bedroom. And despite Magnus' reassurances that he really wasn't shy about being seen on a date with a man, Alec would always check in to make sure that Magnus was feeling ok. 

Magnus supposed it was lucky that Alec didn't have angel blood anymore, because he couldn't imagine a relationship ever working out between a warlock and a shadowhunter. Some warlocks used glamours to hide the fact that they didn't age when in relationships with mundanes or broke up with them after a few years so their secret wouldn't be discovered. Magnus, on the other hand, had always believed in telling his partners the truth eventually, even if most of them didn't stay after that. If things started getting serious and it seemed that Alec wasn't just looking for a fling, then Magnus would have to think of a way to break the news gently. He wasn't looking forward to it.

But this was only their third date and he didn't have to worry about that yet. They had a great time bowling, Magnus letting Alec show off a little before easily sweeping the board with _his_ skills, and he'd had to resist dropping a comment about being around when they'd built the first indoor bowling alleys in New York City in the 1840s. Alec had been a very gracious loser and had insisted on paying for dinner before walking him home. 

"I still can't believe you managed to throw a perfect twelve strikes in a row," Alec commented. 

"Just one of my many hidden talents," Magnus replied with a smile. 

"Yeah? What other secrets have you been hiding from me, Mr Bane?" Alec was just teasing, but it hit Magnus like a bucket of cold water. 

Magnus swallowed hard, forcing out a smile. "Surely you don't expect me to tell you all my secrets right now."

"You don't trust me?" Alec asked jokingly. 

"I do," Magnus admitted. "I don't know why, but I do."

Alec stopped walking and turned to face him properly, searching his face. "Thank you," he said softly. 

He stepped a little closer. There weren't many people on the street, but Magnus still felt his face heat up. 

"Can I kiss you?" Alec asked. 

"Yes, please," Magnus murmured, tilting his head up and closing his eyes at Alec leaned down to kiss him gently, just a warm press of his lips on Magnus'. 

Magnus felt a pulse of energy at his throat, then there was a loud roaring noise in his ears, and it took him a split second to realise that it wasn't just a sound inside his head. Magnus and Alec broke off from the kiss, both looking around for the source of the sound. To Magnus' horror, at the other end of the alleyway they were standing at he saw a large gash ripping right through the fabric between the worlds, and something large, ugly, and hungry forced its way into their world. Magnus recognised it immediately - it was a Sargatanas demon, a type of succubus, and if one of them had made its way through other nasty things would find their way here as well. Even though he'd been practising to get his magic back in shape, he wasn't sure he had enough magic to both seal the rift between the worlds and kill the demon, but he had no choice - nobody had enough magic to portal anymore, so Magnus was on his own. 

"What the hell is that?" Alec had gone deathly pale.

"Run, I'll deal with this," Magnus said, letting go of Alec. 

"What? No! I can't leave you behind," Alec protested.

"Just go, Alexander. I can't risk you getting hurt," Magnus said, then took a deep breath and dropped his glamour. Alec's eyes widened and Magnus steeled his heart against the hurt when Alec took a step backwards.

He turned his back to Alec so he wouldn't have to watch him run away and crept down the alleyway towards the rift and the demon, trying to focus on drawing up enough power to at least incapacitate the demon temporarily to buy himself time to seal the rift first. The demon was butt-ugly in its true form but ingesting or coming into contact with its venom could cause hallucinations and violent behaviour, and of course an intense spike in libido. Coming through the rift had made it disorientated, but it zoomed in on Magnus immediately when he got near and reared its head to spray him with a dose of its venom so it could feed. Magnus sent a blast of magic at it, sending it flying into a nearby dumpster, then slammed the lid and a ward on it and hurried towards the interdimensional rift, which was glowing the same shade of lurid purple as the portal shard under his shirt - clearly the culprit behind this breach in the world's boundaries. Luckily, the rift was quite a small one, but it would still be quite challenging for him to fix on his own. Then there was a loud thud, and Magnus' heart skipped a beat when he looked up and saw that Alec had followed him down the alleyway and was weighing the dumpster lid shut with whatever rubbish he could get his hands on. 

"You do your thing. I've got this," Alec said, gripping a twisted metal rod he'd picked up with both hands to stand guard over the dumpster even though he was obviously terrified. 

Magnus nodded and turned back to his task. Feeling for the jagged edges of the tear, Magnus dug into them with his magic and _pushed_ , feeding healing magic into it. The demonic dimension wanted to force its way in and spread its corruption, but the boundaries of their world had a natural tendency to mend and protect itself. Once Magnus had pulled the edges close enough, all they needed was a little bit of help to knit back together. 

He was almost done with the rift when there was a deafening bang, and the demon broke through his warding and erupted from the dumpster. Magnus sent one last surge of magic at the mending rift, then staggered towards Alec. The demon was looming over him, but even with no angelic blood in his veins, Alec was standing tall against it and holding his piece of junk metal like it was a seraph blade. 

_Shadowhunter blood breeds true_ , Magnus thought, but Alec was an event planner. Lifting weights in a gym to get nice toned arms wasn't the same as fighting demons every night, and Alec didn't have the speed and reflexes of a shadowhunter. Before the demon could spray Alec with its venom, Magnus sent a desperate blast of magic at the demon and it spun around to face him, recognising him as the bigger threat. Magnus barely had the time to throw his arm in front of his face before he was splattered with demon venom. 

It _burned_. Some of it landed on the side of his face and neck, and even though he was wearing a long-sleeved shirt, the venom seeped through the material to his skin. But he was a warlock, and demon venom had a limited effect on him. As a mundane, Alec was in far greater danger. Magnus looked up just in time to see Alec being thrown into a wall, his makeshift weapon landing with a clatter a few feet away from Magnus. With the last of his magic, Magnus sent it flying at the demon to lodge firmly in its chest. The demon made an odd gagging sound, then slumped against the dumpster in a rather anticlimactic death. 

Magnus' world spun, and he sat down heavily on the ground. He wanted to check on Alec, but he was so dizzy and nauseous that he couldn't get on his feet. 

"Magnus? Magnus, are you ok?" 

Alec's anxious face swam into view, but Magnus recoiled when he tried to touch him. 

"I'm covered in venom. Don't touch me."

"I'll be careful, but we need to get you to the hospital or something," Alec insisted. 

"No hospital. Catarina," Magnus said through gritted teeth. 

Magnus could feel his senses starting to go out of whack; Alec's cologne was choking him, and for a moment he imagined licking a hot stripe up Alec's neck so vividly that he thought that he'd actually done it. He was so hot, but once he took off his jacket he started shivering. Alec put his own jacket around him, and Magnus nearly moaned out loud from the warmth of it and the way it smelled of Alec. His dick was getting hard, and it was taking every ounce of his concentration to keep his body under control. 

"Let's get you home at least and I'll call your friend later, alright?" Alec said soothingly, and helped Magnus to his feet.

\--

Luckily Magnus' apartment wasn't too far away. Alec had to help Magnus into the shower, but even after washing away the venom, Magnus still felt weak and disoriented, his heart racing and senses jangling. He was wearing the loosest, softest clothes he had, but still every brush of fabric against his skin made him want to scream, and his cock was so hard it was aching. Magnus just wanted to crawl into his bed and hope that it would all blow over soon, but even after a century of having nothing to do with demons and magic, he knew it wouldn't be that easy. He had used more magic than he could afford, and magic depletion combined with the effects of the venom and a century of celibacy was sending his body into overdrive. Alec was perched at the edge of his bed waiting for him, fiddling with one of his rings and looking a bit shellshocked, and Magnus was honestly surprised that Alec hadn't run away screaming yet after everything he'd seen. 

"I called your friend Catarina on your phone, and she sort of explained what was going on," Alec said quietly.

Magnus' heart sank. This wasn't how he'd have wanted Alec to learn the truth. He ripped the necklace from his neck and dumped it in a secure curse box on his table, to be destroyed later - he shouldn't have kept it, magic booster or not. "I've got some restorative potions on the shelf. I'll be fine. You should go." 

Alec shook his head vehemently. "Magnus, she said you're going to either get a heart attack or a seizure. Let me help. I want to help."

That wasn't the reaction Magnus had been expecting. "I don't want to get you involved in this mess." Magnus swallowed thickly, struggling to think through the fog overtaking his brain. Sargatanas venom heightened their victims' libido so that they would be more susceptible to the demon's advances, and it was the kind of need that couldn't be satisfied by jerking off. The longer the victims resisted its influence the more painful it got, and Magnus had known of mundanes dying from fighting the venom, but he'd also seen them die from exhaustion and injuries caused by too much sex. Mundanes were just too fragile. "I might hurt you."

"You won't hurt me."

"Did Catarina tell you what I really am?" Magnus demanded, his cat eyes flashing. "I'm the son of a Greater Demon, Alexander. I'm not human. I have hellfire in my veins and blood on my hands, and you have no idea what I'm capable of."

Alec glanced at the vase of preserved roses near the window, then met Magnus' golden eyes squarely and stood up. "I don't care who or what your father is, I care about who _you_ are. And I trust you, too."

He should have moved away, chased Alec off, _something_. But Alec kept coming closer, and Magnus sank into his embrace, too exhausted to fight it any longer. 

"I'm not afraid. If you need me - if you want me to - I'll stay. I'll do whatever you need me to do to help you get through this," Alec murmured. "Just tell me what to do."

Magnus groaned, burying his face in Alec's neck and inhaling deeply, then gave in to the urge to put his lips on Alec pulse point. Alec grunted in surprise, holding Magnus closer, and for a while Magnus thought of nothing except the sounds Alec was making and Alec's hands running down his back. Magnus didn't realise how far gone he was until he slammed Alec onto the bed and Alec winced. 

"I'm sorry," Magnus said, backing off immediately. 

"You didn't hurt me, I'm just a bit bruised from when that thing threw me into the wall just now," Alec assured him. 

Magnus shook his head, hugging himself. The loss of contact was making all his nerve endings scream in protest, but he didn't trust himself to even touch Alec right now, not yet. 

"Bottom nightstand drawer. Take out the cuffs," he said through a clenched jaw. 

Alec raised an eyebrow but obeyed Magnus' instructions, fishing out cold iron cuffs for the wrist and ankles with sigils etched into them.

"Magnus, are you sure?" 

"They'll stop me from using magic. In case I lose control." 

Alec nodded in understanding and took out the tube of lube that he'd spotted in the same drawer. Magnus lay down on his back, putting his arms above his head, and Alec secured his wrists and ankles to the bedposts as quickly as possible. Magnus was already at the end of his tether and Alec knew it. He didn't tease, didn't hesitate - Alec undid the drawstring of Magnus' pants and only pulled them down enough to free Magnus' cock before swallowing him down. Magnus cried out in pleasure, hips bucking as Alec sucked hard on his cock, and he was so on edge that it only took a minute or two for him to come without warning down Alec's throat. Alec choked a little and pulled off, working Magnus through the rest of his climax with his hand, but Magnus was still achingly hard and burning up. 

"Alexander, please. More," Magnus whimpered, desperately thrusting his hips upwards and fighting the chains that held him. 

"Don't worry, I've got you," Alec murmured, quickly stripping out of his clothes. 

He put his mouth on Magnus again, bobbing his head up and down and swirling his tongue around the sensitive head. Alec was good at this, and obviously experienced; he kept one hand loosely circling the base of Magnus cock so it didn't go too deep into his throat but didn't try to hold Magnus' hips down, leaving his mouth and jaw pliant and letting Magnus wreck his mouth, and he had Magnus peaking again so quickly that Magnus' head was spinning. This time, Magnus managed to warn Alec just in time, and Magnus' cock twitched in Alec's mouth as he watched Alec swallow all of his release. 

"Alexander, you're too good for me," he whispered. 

Alec smiled, wiping his mouth with the back of his hand, and came up to kiss him. Magnus groaned when he tasted himself on Alec's tongue, licking eagerly into his mouth and surging upwards to kiss him harder, and Alec eased himself down so that their bodies were touching from chest to thigh. As they rocked against each other, Magnus could feel Alec's hard cock digging into his belly and he had to admit it was a relief - after two orgasms, his head was a little clearer, and he had been a little worried that Alec was just going through the motions to help him get through this. 

"I want this too," Alec assured him, seemingly reading his mind from his expression. "Fuck, you're still so hard."

Magnus felt Alec's hand on his cock holding it steady, and Alec squeezed his eyes shut as he guided himself onto it. Alec must have prepped himself while sucking Magnus off the second time, and he was so slick and tight around Magnus that Magnus was going out of his mind. Even without the demon venom magnifying Magnus' desire and arousal, it would be impossible not to want Alec, not when he was working himself onto Magnus' cock like this: mouth open and slack with pleasure, the redness and puffiness of his lips a reminder that they'd recently been wrapped around Magnus' cock; neck gracefully thrown back to display the marks of Magnus' teeth; a pink flush of exertion from his cheeks all the way down to his nipples; and his cock hard and standing proud, begging to be touched. Magnus wanted to grip Alec's hips and hold him there so he could fuck him properly, but all he could do was buck upwards into Alec as far as his restraints would let him. Alec moaned, reaching behind to spread himself and slowly sank down the last two inches to take Magnus' cock all the way to the hilt. 

Alec leaned forward to brace his hands on either side of Magnus' head and began to roll his hips, letting Magnus' cock slowly slide in and out of him. Magnus moaned in protest, trying to thrust harder into Alec and Alec gasped when Magnus must have accidentally hit his prostate with his mindless bucking. 

" _Fuck_. Magnus, oh my god," Alec moaned as he began to ride Magnus' cock in earnest. 

Magnus could feel another orgasm building, a big one and a magically-charged one. His magic was trapped inside him because of the cuffs, but the room was humming with it like ozone before a storm. The lights began to flicker, and Magnus knew his cat eyes were glowing, but Alec seemed to get even more turned on by that and began to fuck himself even harder and faster on Magnus' cock. 

"Alexander, I'm going to come," Magnus gasped. 

Alec's hand flew to his cock. "Yes, come inside me. Fuck, Magnus, I'm going to-" 

Alec came before Magnus did, bearing down to take Magnus deep and clenching around Magnus' cock as he spilled his release into his fist. Magnus gasped and arched upwards into Alec, then a small magical explosion went off, knocking over things and shattering glass, and Alec cried out again when he felt the warmth of Magnus' come filling his body. 

He slumped against Magnus, both of them shivering and spent, and Magnus sighed with relief when his softened cock slipped out of Alec. The worst of it was over. When Alec had recovered enough, he freed Magnus' wrists and ankles, massaging them to get the circulation going and kissing the red marks made by the cuffs. 

"Let me go get a washcloth to clean us up," Alec said, starting to get off the bed, but Magnus shook his head. 

"I've got this." Magnus snapped his fingers, and Alec jerked in surprise to find himself suddenly clean. 

"I think you've used quite enough magic for one night," he huffed, but settled down beside Magnus. 

Magnus curled into Alec's embrace. "I must say, you're taking this much better than I hoped," he said softly. 

Alec kissed him on the forehead, and when Magnus looked up, Alec was flashing a small lop-sided grin at him. 

"What can I say? I guess I always knew that you were quite magical."

**Author's Note:**

> I'm on twitter @tethysea, come say hi if that's your thing! :)


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